Variable condenser



Sept. 1, 1925. 1,551,661

C. G. HILL VARIABLE CONDENSER Filed May 20, 1922 Patented Sept. 1, 1925.

4 1,551,661 PATENT OFFICE.

CYRUS G. HILL, OF CHICAGO, ILLINOIS.

VARIABLE CONDENSER.

Application filed May 20, 1922. Serial No. 562,324.

To all whom it may concern:

Be it known that I, CYnUs G. HILL, a citizen of the United States, and aresidentof Chicago, in the county of Cook and State of Illinois, have,invented certain new and useful Improvements in Variable Condenser-s, ofwhich the following is a specification. V

This invention relates to variable condensers; it is the object of theinvention to produce a variable condenser particularly useful inconnection with radio work, simple and economical to produce andefficient in use. I

In the drawings, which present an illustrative embodiment of theinvention,

Figure 1 is a sectional plan view of the device.

Figure 2 is a side elevation thereof.

Figure 3 is a plan view of the front of the device. i

The condenser, as a whole, is mounted between the discs 1 andQ, whichmay be of bakelite or other suitable material; it

may be mounted on the rear face of panel 3 (of a radio control box orthe like) with the control knob 4: located in front of the panel forconvenient manipulation.

Referring now to the operating parts of the condenser, I provideinterleaved layers of conductive material and means for adjusting theaverage distance between the interleaved conductive strips, and Ithereby adjustably vary the capacity of the condenser by adjusting thethickness of the layer of air dielectric between the conductive layersthrough j, convenient manual means.

To effect this resultI provide, in the embodiment of the invention hereshown, a pair of spirals 5 and 6, formed of spring brass strips. (fineof these spirals 5 is attached to a terminal 7 (forming a post betweenthe discs 1 and 2) and after a number of convolutions, its inner end isattached to the drum 8 by any suitable means, as by being sprung into arecess 9 and locked therein by a pin 10. The other spring brass strip 6,"attached at its outer end to the terminal and post 11 interleaves withthe strip 5, and at its inner end is The other insulating strip 13 is inall respects similarly located with respect to the brass strip 6.

I have thus provided a multiple spring spiral comprising two conductorsand an interposed insulating layer, the multiple spiral being resilient(somewhat after the fashion of a clockspring). It is obvious that if themultiple spiral is tightened the space between adjacent convolutionswill be reduced, and vice versa -if it is loosened, with the result thatthe capacity of the condenser (comprising'the "conductive strips and theinterposed air dielectric) maybe varied.

The drum 8 is rigidly mounted on a shaft 14 which has bearings in thediscs 1 and 2. At the rear side the shaft 14 extends through the disc 1,is threaded and provided with a nut 15 adjustable by set screw This nutbears on washer 17 which forces the leather washer 18 against the faceof disc 1. thus provided, holds the drum 8 against the tension of themultiple spring in any position to which it may be turned. The

shaft 14, at the front, extends forwardly a distance to clear the panel3 and is there provided with the knob 4: suitably secured thereto.

Further details 'of construction may be described as follows: the twoterminals 7 and 9 are recessed and threaded at their forward ends, andthe disc 2 is attached thereto by screws 19, this construction beingadapted at both ends of all the additional posts 20 which support andspace the discs 1 and 2. The terminals and posts 7 and 9 at their rearends are provided with shoulders 21 and extensions 22 passing throughthe disc 1 and threaded to receive the thumb nuts- 23 whereby wires maybe attached thereto. A cylindrical casing 24 fits in grooves in theinner face of the discs and houses the condenser parts. The completecondenser may be secured to panel 3 by the screws 25 passing through thepanel.

In operation, turning the knob 4 tightens or loosens the multiple springspiral, there The adjustable friction,

by varying the average space between the conductor strips and thusvarying the capacity of the condenser by varying the average thicknessof the layer of air dielectric intervening between adjacent convolutionsof the mutliple coil. The friction means, comprising the nut andassociated posts, maintains the adjustment.

\Vhile I have shown herein a separate strip of non-conductive material,I may substitute therefor a strip attached to one or both faces of each,or both faces of one, strip 5 and 6, or I may coat one or both faces ofeach strip 5 and 6 (or both faces of one strip) with an elasticinsulating varnish.

The invention, in its broader aspects, is not limited to the particulardetails here described and shown for illustrative purposes,

but is more properly defined in the appended claims:

L'A variable condenser comprising a plurality of spirally woundresilient conductors, a pair of terminals each in contact with half ofsaid conductors, and rotatab'ly adjustable means for simultaneouslyvarying the average distance between adjacent conductors.

2. A variable condenser comprising in combination a pair of terminals, aplurality of continuous layers of flat conductive material inelectric-contact with each terminal, said layers being interleavedsubstantially in spiral form, and rotatably adjustable means forsimultaneously varying the average distance between the adjacent layers.

3. A variable condenser comprising a resilient coil of conductive anddielectric material arranged in intervening layers, a layer ofdielectric material being interposed between two layers ofconductivematerial, means for tightenin'gor loosening said coil to adjust thespace between the layers of conductive material. 7' n 4.. A variablecondenser comprising amultiple spiral formed of interleaved resil- 1entconductive material, having its convolutions insulated from each other,and means for adjustably tightening or loosening the multiple spiral tovary the space between the convo-lutions thereof. v

5. A variable condenser comprising in combination a multiple spiral madeup of two spirals of conductive material and an interleaved spiral ofnon-conductive mate rial and means for adjusting the average spacebetween the convolutions of the spirals of conductive material byrelative rotation of spaced portions of said spirals.

6. A variable condenser comprising a casing, a pair of terminalstherein, a pair of spiral spring metal strips attached each to aterminal and interleaved with each other, a drum at the center of thespirals and attached to each thereof, a dielectric between theconvolutions of said spring metal spirals and manual means for turningsaid drum to tighten or loosen the convolutions of said spiral strips.

7. A variable condenser comprising a casing, a pair ofterminals'therein, a pair of spiral spring metal strips attached each toa terminal and interleaved with each other, a drum at the center of thespirals and attached to each thereof, insulating means betweentheadjacent convolutions of said spring metal spirals and means for turningsaid drum and means for maintaining said drum in adjusted position.

8. variable condenser comprising a casing, a pair of terminals therein,a pair of spiral spring metal strips attached each to a terminal andinterleaved with each other, a drum at the center of the spirals andattached to each thereof, dielectric between the adjacent convolutionsof said spring metal spirals and manual means for turning said drum andmeans for maintaining said drum in adjusted position, in-

.cluding friction means for preventing the :rotation thereof.

In witness whereof, I hereunto 1 subscribe my name this 15th day of May,A. 1)., 1922.

CYRUS G. HILL.

